7 Special Senses

Special senses (extension of the nervous system):

• sight

• hearing

• balance

• smell

• taste

Structures of the Eye:

• each eye is located in a body cavity (socket) in the skull called the orbit

• upper and lower movable folds of skill called the eyelids protect the eyes

• tears secreted by the lacrimal gland lubricate eyes

Functions of the Eye:

• observing light, perceiving depth, and serving as the organ of vision

• maintaining balance by detecting changes in posture when we move

conjunctiva

mucous membrane that lines the eyelids and outer surface of the eyeball

orbit

bony cavity of the skull that encases the eye

lacrimal glands

glands that secrete tears

lacrimal ducts

channels that carry tears to the eyes

tarsal glands/ meibomian glands

oil glands along the edges of the eyelids that lubricate the eye

aqueous humor

watery fluid that fills the anterior chamber of the eye between the lens and the cornea

cornea

transparent outer covering of the anterior portion of the eye

iris

colored muscular part of the eye located behind (posterior to) the cornea that allows light to pass through

sclera

tough fibrous outer layer of the eye (the white of the eye) that extends from the cornea to the optic nerve

choroid

middle layer of the eye that contains blood vessels

lens

transparent structure behind (posterior to) the pupil that bends and focuses light rays

pupil

opening in the middle of the iris through which light passes

vitreous humor

jelly-like fluid that fills the posterior chamber of the eye between the lens and the retina

fundus

posterior portion of the interior of the eyeball, visible through the ophthalmoscope

optic nerve (CN I)

cranial nerve I that carries impulses from the retina to the brain to provide the sense of sight

retina

innermost layer of the eye that contains visual receptors (rods and cones)

blephar/o

eyelid

conjunctiv/o

conjunctiva

cor/e, cor/o, pupill/o

pupil (of the eye)

corne/o, kerat/o

cornea

cry/o

cold

dacry/o, lacrim/o

tears, lacrimal (tear) duct

dipl/o

double, two

ocul/o, ophthalm/o

eye

opt/o

vision, eye

phot/o

light

presby/o

related to aging

retin/o

retina

scler/o

hard, sclera

ton/o

tension, pressure

bi-, bin-

two, twice

choroido-

the choroid

icetero-

jaundice (yellow)

-ectasia, -ectasis

dilation, stretching

-lysis

destruction, breakdown, separation

-malacia

softening

-meter

instrument for measuring

-metry

measurement of

-opia, -opsia

vision

-pexy

surgical fixation

-phobia

abnormal fear of, aversion to, sensitivity to

-plasty

surgical repair, reconstruction

-plegia

paralysis

-ptosis

prolapse, drooping, sagging

-rrhea

flow, discharge

-scopy

process of examining, examination

-spasm

involuntary movement

-trophia

to turn

Accommodation

ability of the eye to adjust focus on near objects

Binocular

pertaining to both eyes

Blepharal

pertaining to the eyelid

Conjunctival

pertaining to the conjunctiva

Corneal

pertaining to the cornea

Intraocular

within or inside the eye

Iridal, Iridial

pertaining to the iris

Lacrimal

pertaining to tears

Ocular, Ophthalmic

pertaining to the eye

Optic

pertaining to vision

Pupillary

pertaining to the pupil

Retinal

pertaining to the retina

Scleral

pertaining to the sclera

Amblyopia

poor vision, usually in only one eye, caused by abnormal development of the visual areas; also known as ‘lazy eye”

Astigmatism

distorted, blurry vision caused by abnormal curvature of the cornea and/or lens

Blepharitis

inflammation of the eyelid

Blepharoptosis

drooping of the eyelids, also shortened to ptosis

Blepharospasm

contraction of the muscles surrounding the eye, causing uncontrolled blinking

Cataract

clouding of the lens of the eye, causing poor vision

Chalazion/ Meibomian cyst

inflammation of the eyelid from a blocked tarsal gland

Color blindness

deficiency in distinguishing some colors

Conjunctivitis

highly contagious inflammation of the conjunctiva; commonly known as pinkeye

Dacryoadenitis

inflammation of the lacrimal gland

Dacryocystitis

inflammation of the lacrimal sac

Dacryolith

stone in the lacrimal sac or lacrimal ducts

Dacryorrhea

excessive discharge of tears

Detached retina

separation of the retina from the choroid in the back of the eye; can be caused by injury, tumor, or hemorrhage

Diabetic retinopathy

degenerative changes of the retina caused by diabetes mellitus; may lead to blindness

Diplopia

double vision

Exophthalmos/ exophthalmus

abnormal protrusion of one or both eyeballs

Glaucoma

group of diseases of the eye characterized by increased intraocular pressure that damages the optic nerve

Hordeolum

infection of an oil gland of the eyelid; commonly called a sty

Hyperopia

farsightedness

Iridomalacia

softening of the iris

Iridoplegia

paralysis of the iris

Iritis

inflammation of the iris

Keratitis

inflammation of the cornea

Keratomalacia

softening of the cornea, usually associated with severe vitamin A deficiency

Macular degeneration

deterioration of the macula (the central part of the retina), causing impaired central vision; most commonly related to advancing age

Did you know…

as eyes age, the shape of the lens changes. In infancy, the lens is more spherical; and in the elderly, the lens is more flattened. This flattening is what causes the need for prescription lenses.

Nyctalopia

poor vision in reduced light or at night; commonly called night blindness

Nystagmus

involuntary rhythmic movements of the eye

Ophthalmalgia

pain in the eye

Ophthalmia

condition of the eye characterized by severe conjunctivitis

Ophthalmopathy

any disease of the eyes

Ophthalmoplegia

paralysis of the eye muscle(s)

Photophobia

extreme sensitivity to light

Presbyopia

impaired vision caused by old age

Pterygium

growth of conjunctival tissue over the cornea; usually associated with prolonged exposure to ultraviolet light